The protection of well water.
We will start with what people do not want to hear first and go from there.
If you are on a well, I would never add man made fertilizer or insecticides or herbicides to the lawn. Period.
It will get into the well.
A well draws in a manner that can be almost considered conical. That deep water "aquifer" that seems to be a prevalent notion is not all that is talked about.
Bedrock is not a solid impermeable mass that keeps surface water from deep water. It is full of cracks and crevices and areas where the water from top goes down into the water bearing rock.
The recharge area for a well can be describe as a direct relation between its depth and yield. The deeper a well or the more yield it has, the further the draw range of the well.
Rain water provides a good portion of the water that comes from a well, so what you put on your lawn, you drink.
Soils filter out a great number of things - bacteria, very quickly and many common items that are nutrient based.
Gasoline and oils, not at all. And pesticides. even though they are not generally water soluble, will slowly find their way to a well.
If the well is near a river, what is in the river, what is dumped in the river, will also find its way into the well. A river will skew the conical draw of a well with it giving more to the well than the rain.
Then there are septic systems, usually put on the other side of a house, but septic systems are considered the primary recharge for wells. All the normal stuff is well filtered out by 25 feet, but what if you clean out your oil based paint brushes in the slop sink leading to the well? Right into your drinking water.
How far is this influence of a recharge zone? Deepends on the draw of the well, the depth and yeild, but it can be up to 200 yards, easily.
What about a dump?
It could effect wells near it.
Here though is also where the idea of an "aquifer" comes to play. Ground water and subsurface water slowly seeps in a down slope manner.
In Connecticut, the Glaciers created a general movement North to South.
You look to the south of a dump for the worst of the situation here.
How much well contamination is from homeowners? Most.
How much from dumps? Too much.